Telephone system



Jan. 27, 1942. c. w. HALLIGAN E-r AL `TELEPHONE.sYsTEM Filed March 1.l 1939 c. nf. HALL/GAN /Nl/ENTORS. WH 7 HOLDEN WMWMMMY ATTORNEY NN m ments, however, have disadvantages;

Patented Jan. 27, 1942 UNITED STATES PATENT 01u11(11511,:1;A

, y 2,271,072 I I TELEPHONE SYSTEM v Clair W. I-Ialligan, New York, and William H. T. v Holden, Long Island City, N. Y., assignors to Y Bell Telephone Laboratories, Incorporated,- v v g, New York, N. Y., a corporation of New York v f Application March 1, `1939,' serial No.y 259,078'

' (ci. 17e- 7.1) v

8 Claims.

This invention relates to telephone systems and particularly to those in which message registration is utilized for the purpose of charging the subscribers for the service rendered.

The objects of the invention are to obtain a more reliable performance of the subscribers message register, particularly where successive operations are required during conversation; to enable repeated operations of the register without thefuse of excessive currents and voltages and without interfering with the operative condition of associated apparatus; and otherwise to improve systems of this character.y

It is often desirable in automatic telephone systems to operate the subscribers message register at repeated intervals throughout the conversational period as a measure of the charge to be made for the call.` And, for reasons of economy, it is also desirable to apply the meterloperating impulses to the sleeve or control conductor of the line to effect the successive operations of the register.

,perienced in obtaining the successful operation and release of the register in response to each metering impulse without disturbing the operative condition of the cut-off relay. Several arrangements have been suggested in the past for meeting this diiiiculty, IIhese prior arrangeusually they require the application of excessive voltages to the sleeve conductor, which interfere with the successful operation of the associated equipment and produce excessive currents in the relay windings.

According to the present invention, the objections above mentioned are overcome by a register-operating circuit arrangement in which the control electrodeA of a three-element discharge device is connected to the sleeve conductor ofthe line, and the message register is connected in a vsleeve conductor to ionize the discharge device and bring about the flow ofroperating currentinthe separate anode circuit, thev alternating current source serving to quench" the anode current discharge immediately that the booster batteryimpulse is removed from the sleeve conductor; Since the voltagerequired to ionize the device is comparatively low, it is possible to limit l the potential applied to the sleeve conductor Ato safevalues, although the voltage required `to operate the register and maintain the anode-discharge iscomparatively high. This is` true y--iirl the present arrangement because the anode circuit containing the messageregister is entirely -separate from the sleeve circuit. vThese repeated :applications of booster battery potential tothe sleeve conductor do not disturb 'the cut-offrelay `anddo not increase the current flowing through said relay 'sufficiently to produce overheating.

, Thesev and other features of theinvention lwill "be discussed more fully in detail in the following' specification and will also be set forth in the apjpended claims. v

"The' drawing accompanyingthe specication illustratesthe invention embodied in an auto'- matic telephone system, and for the sake of clearnessall parts of the system not essential to :an vunderstanding of the ji'nve'ntion have been v omitted. 4 f 'i Referring to thedrawing in particular, it is assumed that the subscribers lines, such as line ,appear in the contact-banks oi a plurality of line-iinderswit'ches and also inthe banksv of va plurality of connectorV switches. The iinder svvitchesl seize the lines fwhen they are calling,

' and. the connector switches Care directed tothe 'terminalsv of lines that are being called, "When a lineffinder F seizes a calling line, it extends that line through to anl associated rst selector switch S. `The switch Sand vother succeeding switches are! operated selectively in accordance with impulses transmitted by the` calling subscriber to extend theconnectiontoward the desired called line. v. y

l The subscribers line l, and the same is true of other subscribers lines, is yequipped withthe usual individual line relay 2 and aout-ofi relay'3. A lso the'line I, being a message rate line, is providedwith an individual message registeri4, which may be operated at periodic intervals during the time-the subscriber of line l is conversving,l the duration of the successive periods"` and lthe number of times the register is operated'in 'each period dependingupon the zone int'ojwliich the call has been extended. Associatedwith the register 4 is a discharge tube 5 of the three-elecf, trode gas-,filledtype,Y togetherv with thev necessary circuit elements--ffor controlling .the repeated operation of the register in accordance with the principle of this invention.

The circuit T, interconnecting the line finder F and the first selector S, is sometimes known as a message-register trunk and includes the necessary apparatus for determining the rate of operation of the message register and for applying a source of booster battery potential tothe sleeve conductor of the line to bring about the operation of the register in accordance with the'desired rate.

The selector switch S, either directly or through other switches, has access to local circuits and also to trunks T--I outgoing to distant zones and to different central offices therein. It is common practice to equip these trunkswith a control mechanism 6 which identies the zone into which the call is being extended and establishes zone information in the message register trunk T to determine the rate of charge while conversation is taking place. The mechanism for recording the zone information in the trunk T is not illustrated, sinc'e it is old and well known in the art. There is shown, however, a timecontrolled selector switch S-I, which Vmakes 'a revolution at periodic intervals during the conversation and connects the booster battery source to the sleeve conductor a number of times depending upon the zone information recorded in the message registertrunk T.

The outgoing trunk T-I extends to a distant oice where it has access through selector switch S2, and possibly other selectors, and a connector switch C-I to the called line 1.'

Although the invention is not limitedfto any particular type of central oiiice system, it may be assumed that the system illustrated employs the well-known step-by-step switches. Also the message-register trunk T andk the associated equipment, whereby a subscribers register 'is operated in accordance with the zone intot Vwhich a call is extended and in accordance with the duration of conversation, may in geiiej'ral be the same as that disclosed and described in the reissue patent to Stokely 19,491 of March 5, 193,5. The discharge tube 5 Vmay be of anysuitable type. Such as the` well-known three-element cold-cathode gas-filled tube.

Considering now the details of the subscribers line circuit, it will be noted that the sleeve con- F ductor 8 of the line I is connected through a high resistance 9 to the control element I0 ofthe the tube, is connected through the winding of the message register 4 to the negative pole `of a biasing battery l2. 'Ihe anode I3 of thev tube is connected through a resistance I4 and the secondary winding of transformer I5 to the 'positive pole of the anode battery I6. VThe anode I3 and the cathode Il form the main discharge gap of the tube, and the operating or workcircuit of the tube includes this gap, the battery I6, the secondary winding of transformer I5, the resistance I4, the message register 4 and the biasing battery I2. The primary Winding of the transformer I5 is connected to a Asource of alternating current I'I of any suitable frequency,

The voltage supplied by batteries I6 and I'2 is insufficient to cause discharge across the main gap in the absence of ionization of the control gap. This voltage is, however, sufficient to maintain the discharge across the main gap once the tube is ionized, although ionization across the the alternating current source is sufficient to quench the discharge across the main gap when its polarity is in opposition to the voltage supplied by batteries I6 and I2. Consequently, the main gap is quenched at each half cycle of the alternating potential. So long as the control gap remains ionized the discharge is resumed across the main gap on each alternate half cycle of the alternating potential, but the main gap fails to resume its discharge as soon as ionization ceases across the control gap. During the control gap may have ceased. voltage of '75 discharge intervals across the main gap current flows in the operating circuit through the winding of the register 4 and into the condenser I8. During the oscillations or half cycles While the main gap is quenched the condenser I8 discharges through the winding of the register 4, thus serving to maintain a substantially constant oW of current through the register notwithstanding the successive interruptions in the flow of current across the discharge gap.

The operation of the system will now be described,'assuming for that purpose that the subscriber of line VI Wishes to holdY a conversation with the subscriber of line 1 `'located ina distant central office zone. When the calling subscriber'removes his receiver the line relay 2 operates in a circuit from battery through the right winding thereof, inner left contact of relay 3, thence over the loop of the line and returning through the outer left "contact of relay3 and the left Winding of relay 2 to ground. Relay 2 lapplies ground potential vto the 'start wire I9 to initiate the hunting operation of the line finder F. As soon as the iinder F places its brushes on the terminals of the `calling line I, the finder comes to rest, and a circuit is closed as follows for operating the cuteoff relay 3: Ground through the normal contacts of relay 23, contacts `o'f the Vre1ay2`l, which operates when the line 'is seized, sleeve conductor 22' of the trunk circuit 'T, thence through the sleeve brush 23 and sleeve terminal 24 tothe sleeve or control conductor 25 of the subscribers line, through the right contact of relay 2 to the sleeve or control 'conductor 8, winding of the cut-dif relay 3 'to battery. -Relay 3 operates and closes a locking circuit through its right contact to the grounded conductor 25 and yopens the operating circuit of relay 2, permitting the latter relay to release. The connection of groundV potential to the vconductor 18 places the voltage of the biasing battery I2 across the control gap III- II of the tube 5, but this potential is insufficient to cause ionization of the tube. l

The calling subscriber proceeds to operate his impulse dial 2G to control the operation of the Switchs, and possibly other switches in the local office to select trunk T-I Aoutgoing to 'the distant'l called office and to control the switches 'Sg-72 and C--I therein to `establish connection with the called line 1. During the establishment of the connection the message register trunk `T receives the information necessary V'to determine the rateiof charge for lthe call. lWhen the called subscriber answers, current is reversed kover the connection, andthe polarized relay 21 operates to condition the circuits of the trunk T and to initiate the charging operation, which 4continues 'through theconversational period. At suitable intervals during this""perio'd"the "timing switch S-I is caused to ystepthrough a complete rotary Amovement to "apply impulses' 'ofk booster battery to the sleeve circuit'l As the "selector 'S`I 'steps over its terminals it encounters in response to the first metering impulse applied ground potential on one or more of the conductors 28, depending on the zone information registered in the trunk T, and relay 20 operates and releases a corresponding number of times.

vFor a better understanding of the detailed cirlreissue patent to Stokely, No, 19,491.

Each time relay 20 operates it substitutes the positive pole of the booster battery 29 for the yground connection at the normal contact of the relay. The circuit for applying the booster battery 29 may be traced from the positive pole of said battery, ballast lamp 38, resistance 3|, closed contacts of relay 20 thence to the control conductors 25 and 8. Since the booster battery 29 and the exchange battery connected to the 'terminal of the cut-off relay 3 are in series-aiding relation, the application of the booster battery to the control conductor 25 causes some increase in the flow of current through the Winding of the cut-off relay 3, thus insuring that this relay will be maintained in an operated condition.

Also, the'rst application of the booster battery 29 to the control conductor 8 raises the positive potential of the control electrode I8 to a value commensurate with the voltage of the battery This positive potential on the control electrode I0, being opposite in polarity to the potential applied to the cathode I I by the biasing battery I2, results in a potential difference across the control gap which is sufficient to ionize the tube. As soon, following the ionization of the control gap, as the potential from vthe source Il f is of a polarity to aid the anode battery I6, a discharge occurs across the main gap of the tube,

ance I4, anode I3, cathode II, winding of register 4 to the negative pole of battery I2 and thence to ground. Since condenser I8 is in parallel with the register 4, said condenser also receives charging current from the batteries I6 and I2.` The register 4 operates in this lcircuit and scores a 'charge on the number wheel mechanism.

During the brief interval that the relay 20 is maintained energized and battery potential is applied to conductor 8, the alternating current vsource Il will, according to its frequency, undergo a series of alternations. At each alternate oscillation of this source, the potential induced in the anode circuit opposes the batteries I6 and l The release of relay 28 replaces the ground potential to ,insure the continued holding of the cut-off relay 3. vThe removal of the booster potential from conductor 8 lowers the voltage across the control gap to its original value, and the ionization ceases. Accordingly, on the next opposing alternation of the source II the main discharge gap is quenched and remains so, and after a brief interval th-e message register 4 releases.

Thus the register `Il is operated and released 'and current flows Yin the operating circuit traceyable from the positive pole of battery I6 through I the secondary winding of transformer I5, resistate the message register.

tothe sleeve or control conductorsv of the subscribers line, and the cut-off relay 3 is maintained securely operated during this registration.

.And for each' succeeding application of booster vpotential throughout the conversational period the register is operated and released, and the cutoifrelay remains operated.

When the conversation isv completed, the subscribers replace their receivers on the switchhooks, and the operated equipment is restored to its normal condition in the usual manner.

Since the control gap of the tube ionizes when a sufficient voltage is applied across the control electrodes and requires a relatively small value of current to maintain the discharge, and since the source for operating the register is connected in the operating circuit of the tube, it is possible to obtain successive operations of the register without applying high voltages to the control conductor. In other Words the use of a local circuit through the register and the main gap of the tube makes it possible to apply the relatively high voltages requiredl bythe resistance of the register and to maintain the main gap discharge and at the same time to isolate the sleeve or control conductor from these high voltages.

Another advantage of the circuit diclosed is the safeguard it provides against false operation of the register on surges in the sleeve conductor. For example, if direct current were used in the anode circuit of the tube, momentary surges of voltage, suflicient in value to ionize the control gap, would cause false operation of the register. But with alternating voltage superimposed on the anode circuit transient surges from the sleeve conductor cannot maintain conduction in the anode circuit for a suflicient number of cycles of the alternating voltage source to charge the condenser to a voltage high enough to oper- The use of the alternating potential source in the anode circuit thus guards the register by adding, in effect, an interval of time during which the register does not recelve enough current to operate.

What is claimed is:

l. The combination in a telephone system of a line having two talking conductors and a control conductor, a discharge device having `electrodes forming a control gap and a main discharge gap, a circuit for said control lgap connected to said control conductor, an operating circuit for said discharge device includingy said main gap, a source of potential, means operative at' successive intervals for applying said source to said control conductor for relatively short periods of time to produce discharges across the control gap, a source in said `operating circuit for causing the flow of current across said main gap and through said operating circuit in response to the discharge of said control gap, said last-mentioned source being of sufiicient Voltage to maintain said current iiow after' discharge has ceased in said control gap, a message register for said line connected in said operating circuit and responsive to the flow of current theref in, and means` for quenching the discharge of said main gap to terminate the flow of current in said operating circuit.

2. The combination in a telephone system of a subscribers line having talking conductors and a control conductor, a discharge device having a control electrode and a main discharge gap, an operating circuit for said device including said main discharge gap, a source of potential, means trol conductor lfor applying an increase of potential at periodic intervals 'to said control electrode, a source of current responsive to each application of increased potential to said control electrode for causing a ow of current across said 4main discharge gap and through said operating circuit, said source of current being of sufficient voltage to maintain the discharge of said main gap, a message register responsive to the flow of current in said operating circuit, and means for quenching the discharge of said main gap upon the removal of each application of increased potential to said control electrode to permit the release of said message register.

3. The combination in a telephone system of Aa subscribers line having talking conductors and a control conductor, a discharge device having a Vcontrol electrode and a main discharge gap, an operating circuit for said device including said main discharge gap, a source of current in said `operating circuit, a source of potential, means including said source of potential and said control conductor for applying an increase of potential at periodic intervals to said control electrode to cause the flow of current from said nrst-mentioned source across said main discharge gap, the potential of said source in the operating circuit being sunicient to maintain the discharge across said main gap, a message register connected in said operating circuit and responsive'to the flow of current therein, and a source of alternating current connected to said operating circuit serving on alternate oscillations to oppose the firstmentioned source of current in said operating circuit to quench the discharge across said main gap.

4. The combination in a telephone system of a subscribers line having talking conductors and a control conductor, a discharge device having a control electrode and a main discharge gap, an operating circuit for said device including said main discharge gap, a source of current in said operating circuit, a source of potential, means including said source of potential and said control conductor for applying an increase of potential at periodic intervals to said control electrode to cause the flow of current from said first-mentioned source across said main discharge gap, the potential of said source in the operating circuit being suicient to maintain the discharge across said main gap after the removal of the increased potential from said control electrode, a message register connected in said operating circuit and responsive to the flow of current therein, and a source of alternating current inductively connected to said operating circuit .and serving on alternate oscillations to reduce the potential applied to said main discharge gap below the value sufcient to maintain the discharge thereof.

5. The combination in a telephone system of a line having talking conductors and a control conductor, a discharge device having a control electrode and a main discharge gap, a relay connected to said control conductor, an operating "circuit for said device including said main ldischarge gap and excluding said control conductor,

in'cluding said source' of potential and said cona source of current in said operating circuit, means for applying a potential to said control conductor to operate said relay Without causing the discharge of `said device, means for repeatedly increasing the potential on said control conductor and the control electrode of said device to cause discharge current to now across said main gap fromv the source in said operating circuit, and a message register for the line included in said operating circuit and responsive to the flow o'f current therein.

6. The combination in a telephone system of a line having talking conductors and a control conductor, a discharge device having a control electrode and a main discharge gap, a cut-oi relay connected to said control conductor, an operating circuit for said device including said main discharge gap and excluding said control conductor, a source of current in said operating circuit, a source of potential and means for applying the same to said control conductor to operate said relay, said source being insuii'icient to cause the discharge of said device, a second source of potential, means for substituting said second source for said rst source of potential to hold said relay operated and to raise the potential of said control electrode sufficiently to cause discharge current to flow from said source in the operating circuit across said main discharge gap, and a message register in said operating circuit responsive to the flow of current therein.

7. The combination with a telephone line having an auxiliary conductor for control purposes of a space discharge device having electrodes forming a control gap and a main gap, a circuit for said control gap including said auxiliary conductor, an operating circuit for said device including said main gap, a source of potential, means for applying said source repeatedly to said auxiliary conductor to cause the discharge of said control gap, a source in said operating circuit for causing current to flow therein and across said main gap in response to the discharge of said control gap, a message register for said line responsive to the W of current in said operating circuit, and a source of alternat- Ving current for quenching the discharge of said tor to cause the discharge of said control gap, a

source'in said operating circuit for causing current to flow therein and across said main gap in response to the discharge of said control gap, and a message register responsive to the flow of current in said operating circuit.

CLAIR W. HALLIGAN. WILLIAM H. T. HOLDEN. 

